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Analysis of the cracking mechanisms in pre-cracked sandstone under radial compression by moment tensor analysis of acoustic emissions

Wang Guozhu, Luo Xulin, Song Lei, Wang Yu, Han Mouwang, Song Zhaocun, Wu Linjun, Wang Zukun

Archives of Civil Engineering

2022

Vol. 68, nr 3

447--468

Rock masses, especially those with different pre-existing cracks, are prone to instability and failure under tensile loading, resulting in different degrees of engineering disasters. Therefore, to better understand the effect of pre-existing cracks with different dip angles on the tensile instability failure behaviour of rocks, the mechanism of crack initiation, propagation and coalescence in precracked sandstone under radial compression loading is investigated through numerical simulations. The temporal and spatial evolution of acoustic emission (AE) events is investigated by the moment tensor (MT), and the fracture mode of micro-cracks is determined. The results show that the pre-existing cracks weaken the specimens. The strength, crack initiation points and macro-failure modes of the specimens differ significantly depending on the dip angle of the pre-existing crack. For different dip angles of the pre-existing cracks, all the micro-cracks at the crack initiation point are tensile cracks, which are dominant during the whole loading process, and mixed cracks are mainly generated near the upper and lower loading ends after the peak stress. Of the total number of events, more than 75% are tensile cracks; approximately 15% are shear mode cracks; and the remainder consist of mixed mode cracks. The study reveals the instability and failure mechanism of pre-cracked rock, which is of great significance to ensure the long-term stability of rock mass engineering.

Wpływ kształtu rdzenia w dwuwarstwowych modelach przekroju poprzecznego korzeni marchwi na obrazy izochrom

Stopa R., Romański L., Niemiec A.

Inżynieria Rolnicza

2006

R. 10, nr 4(79)

215-222

W pracy zaprezentowano rezultaty elastooptycznych badań dwuwarstwowego, płaskiego modelu przekroju poprzecznego korzenia marchwi w próbie promieniowego ściskania. Pomiary przeprowadzono przy użyciu maszyny wytrzymałościowej Instron oraz polaryskopu elastooptycznego. Wyznaczono charakterystyczne obrazy izochrom dla każdego etapu obciążenia oraz dla różnych kształtów rdzenia. Dwuwarstwowy model wykonano z elastomeru poliuretanowego przy zachowaniu praw podobieństwa modelowego.

Introducing of the results of photoelastic investigations of two layer carrot root flat model in test of radial compression among two parallel plates. Photoelastic investigation were leading in crossing light by using of linear polariscope. For three shape's of core characteristic isochroma pattern pictures were determined. Two layer epoxy resin model were made at the maintenance of model similarity for barks and core of carrot root conditions.